// #include <cstdlib>
// db rnd() {return 1.0L * rand() / RAND_MAX;}
// db rnd(db l, db r) {return rnd() * (r - l) + l;}

#include <random>
#include <chrono>
std::minstd_rand rdIns(std::chrono::steady_clock::now()
    .time_since_epoch().count());
int rnd(int l, int r) {return std::uniform_int_distribution<>(l,r)(rdIns);}
db rnd(db l, db r) {return std::uniform_real_distribution<db>(l,r)(rdIns);}
db rnd() {return rnd(0, 1);}
